JS type argument defaulting should give implicit 'any' error

TypeScript Version: 3.0.0-dev.20180711

Code

tsconfig.json

{
    "compilerOptions": {
        "strict": true,
        "allowJs": true,
        "checkJs": true
    }
}

a.js

/**
 * @template T
 * @return {T}
 */
function f() { return x; }
const x = f();

Expected behavior:

Error somewhere that x is implicitly any.

Actual behavior:

No error.

[sandersn]

This isn't caused by the circular reference. It's the implicit defaulting of type arguments to any in JS. T can't be inferred since there aren't any parameters or contextual types, it defaults to any. We need to add an implicit any error manually.

[sandersn]

Here's a non-circular repro:

/** @type {any} */
const y = 1
/**
 * @template T
 * @return {T}
 */
function f() { return y; }
const x = f();